Unlocking High Capacity and Fast Na<sup>+</sup> Diffusion of H<sub>x</sub> CrS<sub>2</sub> by Proton-Exchange Pretreatment.

Stiles, Joseph W; Soltys, Anna L; Song, Xiaoyu; Lapidus, Saul H; Arnold, Craig B; Schoop, Leslie M · Adv Mater · 2023

basic_science · Level V

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Abstract

This study presents a new material, "H<sub>x</sub> CrS<sub>2</sub> " (denotes approximate composition) formed by proton-exchange of NaCrS<sub>2</sub> which has a measured capacity of 728 mAh g<sup>-1</sup> with significant improvements to capacity retention, sustaining over 700 mAh g<sup>-1</sup> during cycling experiments. This is the highest reported capacity for a transition metal sulfide electrode and outperforms the most promising proposed sodium anodes to date. H<sub>x</sub> CrS<sub>2</sub> exhibits a biphasic structure featuring alternating crystalline and amorphous lamella on the scale of a few nanometers. This unique structural motif enables reversible access to Cr redox in the material resulting in higher capacities than seen in the parent structure which features only S redox. Pretreatment by proton-exchange offers a route to materials such as H<sub>x</sub> CrS<sub>2</sub> which provide fast diffusion and high capacities for sodium-ion batteries.